A system for controlling an automatic machine, a motor and an industrial robot has a control unit for controlling operations of the automatic machine, the motor and the robot, and furthermore, has a portable teaching operation unit carried by an operator in a teaching work (which is also referred to as a pendant). For an information transmission of the teaching unit and the control unit, conventionally, a twisted pair wire or an optical fiber has been used as a signal transmission path and a composite cable including a power supply wire to the teaching operation unit (which will be hereinafter referred to as a cable) has been utilized.
As an example, FIG. 7 is a view showing a structure of a conventional robot system described in Patent Document 1. In the drawing, 101 denotes a robot, 102 denotes a control unit for controlling an operation of the robot 101, 103 denotes a portable teaching operation unit, and 104 denotes a cable for transmitting information such as an operation button and an emergency stop between the control unit 102 and the portable teaching operation unit 103. FIG. 8 is a view showing the details of the portable teaching operation unit 103. In the drawing, 105 denotes a housing taking an almost T shape and 106 denotes a hand portion to be gripped by the operator. An operation surface of the housing 105 is provided with a keyboard (or a key sheet) 107 to be operated in the teaching work, an LCD display 108 for displaying various information such as teaching data and a robot position, and an emergency stop switch 109 (corresponding to emergency stopping unit). Moreover, one end of the cable 104 is connected to the housing 105.
When the operator presses down the emergency stop switch 109, emergency stop information is transmitted to the control unit 102 through the cable 104 so that the control unit 102 blocks the supply of power to drive motors (not shown) of the robot 101 and applies a brake (not shown) to each drive motor, thereby stopping the operation of the robot 101 forcibly. Consequently, it is possible to reliably stop the robot emergently with respect to an unintended operation at the worst.
In the conventional robot system described above, the operator is to perform the teaching work while dragging the cable when carrying the portable teaching operation unit 103. For this reason, there is a problem in that a great burden is imposed on the operator and operation flexibility in the teaching is also restricted. Therefore, it has been greatly desired that the cable 104 between the control unit 102 and the portable teaching operation unit 103 is caused to be wireless. For example, Patent Document 2 has described means for implementing an emergency stopping function in a robot system in which a portable teaching operation unit including an emergency stopping unit for blocking the supply of power to drive motors of a robot to bring the robot into an emergency stopping state is constituted to mutually carry out a communication by wireless with a control unit for controlling the robot.    Patent Document 1: JP-A-2000-280193 Publication (Page 7, FIGS. 1 and 2)    Patent Document 2: JP-A-2004-148488 Publication